diff --git a/server/src/main/java/org/elasticsearch/cluster/metadata/Metadata.java b/server/src/main/java/org/elasticsearch/cluster/metadata/Metadata.java
index c6d0944ca6d90..ab56621e748ae 100644
--- a/server/src/main/java/org/elasticsearch/cluster/metadata/Metadata.java
+++ b/server/src/main/java/org/elasticsearch/cluster/metadata/Metadata.java
@@ -397,7 +397,7 @@ private Metadata updateSingleProject(Function<ProjectMetadata, ProjectMetadata>
                     reservedStateMetadata
                 );
         } else {
-            throw new UnsupportedOperationException("There are multiple projects " + projectMetadata.keySet());
+            throw new MultiProjectPendingException("There are multiple projects " + projectMetadata.keySet());
         }
     }
 
@@ -1310,7 +1310,7 @@ private ProjectMetadata.Builder getSingleProject() {
             if (projectMetadata.isEmpty()) {
                 createDefaultProject();
             } else if (projectMetadata.size() != 1) {
-                throw new UnsupportedOperationException("There are multiple projects " + projectMetadata.keySet());
+                throw new MultiProjectPendingException("There are multiple projects " + projectMetadata.keySet());
             }
             return projectMetadata.values().iterator().next();
         }
diff --git a/server/src/main/java/org/elasticsearch/cluster/routing/GlobalRoutingTable.java b/server/src/main/java/org/elasticsearch/cluster/routing/GlobalRoutingTable.java
index 642ea54881acc..e7b707b8993c3 100644
--- a/server/src/main/java/org/elasticsearch/cluster/routing/GlobalRoutingTable.java
+++ b/server/src/main/java/org/elasticsearch/cluster/routing/GlobalRoutingTable.java
@@ -15,6 +15,7 @@
 import org.elasticsearch.cluster.DiffableUtils;
 import org.elasticsearch.cluster.DiffableUtils.KeySerializer;
 import org.elasticsearch.cluster.metadata.Metadata;
+import org.elasticsearch.cluster.metadata.Metadata.MultiProjectPendingException;
 import org.elasticsearch.cluster.metadata.ProjectId;
 import org.elasticsearch.cluster.metadata.ProjectMetadata;
 import org.elasticsearch.common.collect.ImmutableOpenMap;
@@ -134,7 +135,7 @@ public RoutingTable getRoutingTable() {
         return switch (routingTables.size()) {
             case 0 -> RoutingTable.EMPTY_ROUTING_TABLE;
             case 1 -> routingTables.values().iterator().next();
-            default -> throw new IllegalStateException("There are multiple project routing tables [" + routingTables.keySet() + "]");
+            default -> throw new MultiProjectPendingException("There are multiple project routing tables [" + routingTables.keySet() + "]");
         };
     }
 
diff --git a/server/src/main/java/org/elasticsearch/cluster/service/ClusterApplierService.java b/server/src/main/java/org/elasticsearch/cluster/service/ClusterApplierService.java
index 6f1128317a462..b4a626faf79b3 100644
--- a/server/src/main/java/org/elasticsearch/cluster/service/ClusterApplierService.java
+++ b/server/src/main/java/org/elasticsearch/cluster/service/ClusterApplierService.java
@@ -594,7 +594,7 @@ private static void callClusterStateListener(
                     listener.clusterChanged(clusterChangedEvent);
                 }
             } catch (Metadata.MultiProjectPendingException e) {
-                // don't warn, this fills the logs
+                // don't warn, this fills the logs and also slow down applier thread in CI which could cause unrelated failures
                 logger.trace("ClusterStateListener not multi-project compatible", e);
             } catch (Exception ex) {
                 logger.warn("failed to notify ClusterStateListener", ex);